The present invention relates to a system for measuring foreign materials in a liquid to suitably evaluate the cleaning of components used in electron tubes and electronic devices and cleanness of these component after cleaning.
Conventional foreign material measuring apparatuses of this type are classified into an ultrasonic intermittent radiation apparatus for measuring a foreign material having a particle size of 5 to 100 .mu.m and a laser beam radiation apparatus for measuring a foreign material having a particle size of about 0.5 to 60 .mu.m.
The structures of these conventional measuring apparatuses are described in "On-Line Measurement of Fine Particles in Liquid" announced in the "3rd Technical Research Meeting Concerning Air Cleaning and Contamination Control" held in February, 1984.
In these conventional measuring apparatuses for measuring foreign materials, i.e., foreign materials and inorganic ions in a liquid, if bubbles, a gas, or the like is present in a liquid which is subjected to measurement and which is used for cleaning electronic components, bubbles may be attached to a surface of a sensor of the apparatus during measurements of foreign materials. In addition, the bubbles in the liquid are also subjected to measurement, and thus measurement errors are increased It is impossible to accurately measure the sizes of foreign materials and the numbers of inorganic ions and to continuously print out results or display them in a graph.